This invention relates broadly to sheet separators, and more specifically to bottom-type sheet feeders wherein a separating device, such as a suction cup, pulls one edge of a bottom-most sheet away from a main portion of a sheet stack where a sheet-pulling device grips the separated sheet and pulls it from the sheet stack. Still more particularly, this invention is particularly well suited for pull-foot sheet feeding devices of the type described in U.S. Pat. Nos. 4,013,283 and 4,060,228 of Norwood E. Tress and Winston Orsinger. In this respect, the subject matter of those patents is incorporated herein by reference for details of pull-foot sheet feeding devices with which this invention is particularly well suited.
Portions of prior-art devices related to this invention are depicted in FIGS. 1 and 2. In operation of the FIGS. 1 and 2 device, a suction cup 10 is moved upwardly along a circular arcuate path 12 until it makes contact with the lower side of a bottom-most sheet 14 in a sheet stack 16 held in a hopper 18. In this respect, the suction cup 10 is moved along the arcuate path 12 by means of levers 20 which pivot about an axis 22 located on the concave side of the arcuate path 12, approximately at the intersection of the lower side of the bottom-most sheet 14 and a normal position of the end 23 of a breaker plate 23'. As it can be seen in FIG. 2, the levers 20 operate to the sides of the hopper 18 in order to allow the pivot 22 to be at the bottom-most sheet 14 and to leave room for other mechanisms.
In any event, once the suction cup 10 contacts the bottom-most sheet 14 suction is applied through a line 24 and the suction cup 10 is then moved downwardly along the arcuate path 12 by means of the levers 20, drawing the right hand (as seen in FIG. 1) edge of the bottom-most sheet 14 with it. At this point, a separator foot 26 (which is only partially shown in FIG. 1) is moved between the bottom-most sheet 14 and the main portion of the sheet stack 16. Vacuum in the line 24 is then released, thereby disengaging the suction cup 10 from the bottom-most sheet 14 and a segmented roller (not shown) cooperates with the pull foot 26, as it is driven outwardly, to pull the bottom-most sheet 14 with it. A complete description of the segmented roller, and its cooperation with the pull foot 26, is in U.S. Pat. No. 4,060,228 to Tress and Orsinger and that material is incorporated herein by reference.
The reason it is normally desired to place the axis 22 at the bottom-most sheet 14, close to the end 23 of the breaker plate 23', is so that the levers 20 and the bottom-most sheet 14 will pivot on approximately the same axis and the sheet will, therefore, not be put in tension or compression by outward or inward movement of the levers 20.
A difficulty with the prior art described above is that a link 28 connecting the levers 20 with the suction cup 10 obstructs access to the otherwise-available portion of the lower surface of the bottom-most sheet 14. In this respect, it is often desired to place optical sensors below the bottom-most sheet 14 to read instructions as to the disposition of the various sheets from indicia which are printed on the lower sides of the bottom-most sheets 14. However, this link 28 makes this most difficult and, in effect, prevents the use of a limited amount of space on sheets for instruction indicia.
Thus, it is an object of this invention, to provide a mechanism for moving a sheet separating device for a bottom-type sheet feeding assembly which moves the separting device along an arcuate path having an axis which is approximately in the plane of a bottom-most sheet, but which does not obstruct access to large areas of the bottom-most sheet.
It is yet another object of this invention to provide a linkage system for a sheet separating device which is uncomplicated in structure, but yet is accurate and reliable in operation.